Heat pump device

ABSTRACT

In a heat pump apparatus having a refrigerating cycle including a compressor  1 , a gas cooler  3 , a pressure reducing device  5  and an evaporator  7  in which water can be heated by the gas cooler, the compressor  1  comprises a two-stage compression type compressor for leading all or a part of refrigerant compressed to an intermediate pressure at a first stage through a shell case  11  to a second stage, compressing the intermediate-pressure refrigerant to a high pressure at a second stage and discharging the high-pressure refrigerant, and there is equipped a defrosting circuit  33  for leading the intermediate-pressure refrigerant of the first stage of the compressor  1  to the evaporator  7  with bypassing the gas cooler  3  and the pressure reducing device  5.

TECHNICAL FIELD

The present invention relates to a heat pump apparatus using a two-stagecompression type compressor.

BACKGROUND ART

There is known a heat pump type hot water supply apparatus thatgenerally has a refrigerating cycle including a compressor, a gascooler, a pressure reducing device and an evaporator and is designed tosupply water heated by the gas cooler.

This type of apparatus has hitherto used freon containing chlorine(HCFC22 or the like) as refrigerant in a refrigerating cycle. However,from the viewpoint of ozone layer protection, restriction of use offreon has been promoted. Even in the case of freon containing nochlorine (HFC) as substitute refrigerant, it has been specified as arestriction target material in Kyoto Conference on Global Warming (COP3)because it has a high global warming potential.

Therefore, a motion of using materials existing in the natural world inplace of synthetic material such as freon as refrigerant in therefrigerating cycle has been promoted, and particularly use of CO₂refrigerant in the refrigerating cycle has been promoted to beconsidered.

When CO₂ refrigerant is used, a transcritical cycle in which thehigh-pressure side of the refrigerating cycle is transformed into asupercritical state is established, and thus it is expected that a highcoefficient of performance (COP) can be achieved in a heating processhaving a large water-temperature rise-up range as in the case of hotwater supply by a heat pump type hot water supply apparatus.

However, at the same time, the refrigerant must be compressed to a highpressure, so that an internal intermediate pressure two-stagecompression type compressor has been recently used.

In this type of apparatus, devices constituting the refrigerating cycleare frequently disposed as a heat pump unit outdoors, and for example ina winter season or the like, it is frequently required to carry out thedefrosting operation on an evaporator.

In this case, it is general to perform a hot gas defrosting operation inwhich refrigerant discharged from the compressor is supplied to theevaporator with bypassing the gas cooler and the pressure reducingdevice so that the evaporator is heated with the heat of the refrigerantto be defrosted. However, any defrosting circuit to be used when atwo-stage compression type compressor is used has not yet been proposed.

Therefore, an object of the present invention is to solve the problem ofthe prior art and provide a heat pump apparatus which can perform adefrosting operation efficiently when a two-stage compression typecompressor is used.

DISCLOSURE OF THE INVENTION

According to the present invention, a heat pump apparatus having arefrigerating cycle including a compressor, a gas cooler, a pressurereducing device and an evaporator in which water can be heated by thegas cooler, is characterized in that the compressor comprises atwo-stage compression type compressor for leading all or a part ofrefrigerant compressed to an intermediate pressure at a first stagethrough a shell case to a second stage, compressing theintermediate-pressure refrigerant to a high pressure at a second stageand discharging the high-pressure refrigerant, and the heat pumpapparatus includes a defrosting circuit for leading theintermediate-pressure refrigerant of the first stage of the compressorto the evaporator with bypassing the gas cooler and the pressurereducing device.

According to the present invention, the heat pump apparatus as describedmay be characterized by further including a high-pressure defrostingcircuit for leading the high-pressure refrigerant of the second stage ofthe compressor to the evaporator with bypassing the gas cooler and thepressure reducing device.

According to the present invention, the heat pump apparatus as describedmay also be characterized in that refrigerant which works in asupercritical area at a high-pressure side is charged and used in therefrigerating cycle.

According to the present invention, the heat pump apparatus as describedmay further be characterized in that the refrigerant is CO₂ refrigerant.

According to the present invention, the heat pump apparatus as describedmay still further be characterized in that the defrosting circuit isequipped with an opening/closing valve with which the inside of theshell case of the compressor can be vacuum-evacuated.

According to the present invention, the heat pump apparatus describedmay vet further be characterized in that the mixing ratio of oil in theintermediate-pressure refrigerant of the first stage is smaller than themixing ratio of oil in the high-pressure refrigerant of the secondstage.

According to the present invention, a heat pump apparatus having arefrigerating cycle including a compressor, a gas cooler, a pressurereducing device and an evaporator in which water can be heated by thegas cooler, is characterized in that refrigerant that works in asupercritical area at a high pressure side is filled and used in therefrigerating cycle, the compressor comprises a two-stage compressiontype compressor for leading all or a part of refrigerant compressed toan intermediate pressure at a first stage through the shell case to asecond stage, compressing the intermediate-pressure refrigerant to ahigh pressure at the second stage and discharging the high-pressurerefrigerant, and the heat pump apparatus is equipped with a defrostingcircuit for leading the intermediate-pressure refrigerant of the firststage of the compressor and/or the high-pressure refrigerant of thesecond stage to the evaporator with bypassing the gas cooler and thepressure reducing device.

According to the present invention employing a refrigerant that works ina supercritical area at a high pressure side in the refrigerating cycle,the heat pump apparatus may be characterized in that the refrigerant isCO₂ refrigerant.

According to the present invention, the heat pump apparatus employing arefrigerant that works in a supercritical area at a high pressure sidein the refrigerating cycle may also be characterized in that thedefrosting circuit is equipped with an opening/closing valve with whichthe inside of the shell case of the compressor can be vacuum-evacuated.

According to the present invention, the heat pump apparatus employing arefrigerant that works in a supercritical area at a high pressure sidein the refrigerating cycle as may further be characterized in that themixing ratio of oil in the intermediate-pressure refrigerant of thefirst stage is smaller than the mixing ratio of oil in the high-pressurerefrigerant of the second stage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing an embodiment of a heat pumpapparatus according to the present invention;

FIG. 2 is a circuit diagram showing another embodiment;

FIG. 3 is a circuit diagram showing another embodiment; and

FIG. 4 is a circuit diagram showing another embodiment.

BEST MODES FOR CARRYING OUT THE INVENTION

Embodiments according to the present invention will be described withreference to the drawings.

FIG. 1 shows a heat pump apparatus using a two-stage compression typerotary compressor. Reference numeral 1 represents a compressor. To thecompressor 1 are connected a gas cooler (high-pressure side heatexchanger) 3, a pressure reducing device (expansion valve) 5 and anevaporator (low-pressure side heat exchanger) 7 in this order, therebyconstituting a refrigerating cycle.

The refrigerating cycle uses CO₂ refrigerant. The CO₂ refrigerant has anozone depletion coefficient of zero and a global warming potential of 1.Therefore, it has a low load on the environment, has no toxicity and noflammability, and is safe and low in price. When CO₂ refrigerant isused, a transcritical cycle in which the high-pressure side of therefrigerating cycle is transformed into a supercritical state isestablished, and thus it is expected that a high coefficient ofperformance is achieved in a heating processing having a largewater-temperature rise-up range as in the case of hot water supply in aheat pump type hot water supply apparatus.

However, at the same time, the refrigerant must be compressed to a highpressure, and thus an internal intermediate pressure two-stagecompression type compressor is used as the compressor 1.

The internal intermediate pressure two-stage compression type compressor1 has an electric motor portion 2 and a compressing portion 13 driven bythe electric motor portion 2, which are mounted in a shell case 11. Thecompressing portion 13 has a two-stage compressing structure, and itcomprises a first-stage compressing portion 15 and a second-stagecompressing portion 17.

Refrigerant sucked from the suction port 15A of the first-stagecompressing portion 15 is compressed to an intermediate pressure P1 inthe compressing portion 15, and then all the refrigerant thus compressedis temporarily discharged from the discharge port 15B into the shellcase 11. After passing through the shell case 11, the refrigerant ispassed through a pipe path 21, led to the suction port 17A of thesecond-stage compressing portion 17, compressed to a high pressure P2 inthe second-stage compressing portion 17, and then discharged from thedischarge port 17B.

The gas cooler 3 comprises a refrigerant coil 9 through which CO₂refrigerant flows, and a water coil 10 through which water flows, andthe water coil 10 is connected through a water pipe to a hot waterreservoir tank (not shown). A circulating pump omitted from theillustration is connected to the water pipe, and water in the hot waterreservoir tank is circulated in the gas cooler 3 by driving thecirculating pump. The water is heated in the gas cooler 3, and thenstocked in the hot water reservoir tank.

The heat pump apparatus is disposed as a heat pump unit outdoors, andthus it is necessary to remove frost attached to the evaporator 7.

Therefore, according to this embodiment, a hot gas defrosting circuit 33containing a defrosting electromagnetic valve 31 and a bypass pipe 32 isequipped to lead the high-pressure P2 refrigerant of the second stage 17of the compressor 1 to the evaporator 7 with bypassing the gas cooler 3and the pressure reducing device 5. Under the hot gas defrostingoperation, the normally-closed defrosting electromagnetic valve 31equipped in the bypass pipe 32 is opened.

When this defrosting operation is carried out, the high-pressurerefrigerant of the compressor 1 is fed to the evaporator 7 to heat theevaporator 7, thereby removing frost attached to the evaporator.

This embodiment can perform the efficient defrosting operation when theinternal intermediate pressure two-stage compression type compressor 1is used.

Furthermore, since the high-pressure P2 refrigerant is fed to the gascooler 3 while carrying out the defrosting operation, reduction of thetemperature of the gas cooler 3 during the defrosting operation can besuppressed, thereby shortening the time until a steady operation isestablished when a normal operation is resumed.

In the case where this defrosting operation is carried out, thehigh-pressure P2 refrigerant of the compressor 1 is directly supplied tothe evaporator 7, so that there may occur a case where the innerpressure of the shell case 11 is higher than the discharge pressure P2and thus the refrigerant lies up in the shell case 11, or a case whereno vane back pressure of the compressor 1 is applied and thus so-calledvane skipping occurs to induce abnormal sounds. The reason why the innerpressure of the shell case 11 is increased resides in that the excludedvolume of the first stage of the compressor 1 is larger than theexcluded volume of the second stage, or the resistance balance of therefrigerant circulating path is lost. If the refrigerant lies up in theshell case 11, the refrigerant circulation amount is short and thussufficient defrosting cannot be performed.

FIG. 2 shows another embodiment.

Therefore, this embodiment is equipped with a hot gas defrosting circuit133 containing a defrosting electromagnetic valve 131 and a bypass pipe132 to lead the intermediate pressure P1 refrigerant of the first stage15 of the compressor 1 to the evaporator 7 with bypassing the gas cooler3 and the pressure reducing device 5. In this defrosting operation, anormally-dosed defrosting electromagnetic valve 131 equipped in thebypass pipe 132 is opened.

In this case, since the refrigerant of the intermediate pressure P1 islead to the evaporator 7, the inner pressure of the shell case 11 isnever higher than the discharge pressure P2, and thus the pressuredifference therebetween is reduced, so that the refrigerant is preventedfrom lying up in the shell case 11 or occurrence of abnormal sounds fromthe compressor 1 which are caused by vane skipping can be prevented.

Besides, in this type of compressor 1, the mixing ratio ofrefrigerating-machine oil contained in the refrigerant of theintermediate pressure P1 discharged from the first stage and the mixingratio of refrigerating-machine oil contained in the refrigerant of thehigh-pressure P2 discharged from the second stage are different fromeach other. That is, the mixing ratio of the oil contained in therefrigerant of the intermediate pressure P1 is generally smaller thanthe mixing ratio of the oil contained in the refrigerant of the highpressure P2.

Therefore, according to this embodiment, the discharge amount of the oilin the defrosting operation is reduced and the residual oil amount inthe shell case can be sufficiently secured as compared with theembodiment shown in FIG. 1, so that the durability of the compressor 1can be enhanced.

FIG. 3 shows another embodiment.

In addition to the defrosting circuit shown in FIG. 2, this embodimentis further provided with a hot gas defrosting circuit 233 containing adefrosting intermediate electromagnetic valve 231 and a bypass pipe 232for leading the high-pressure P2 refrigerant of the second stage 17 ofthe compressor 1 to the evaporator 7 with bypassing the gas cooler 3 andthe pressure reducing device 5. In this defrosting operation, both thenormally-dosed defrosting electromagnetic valves 131, 231 are opened.This embodiment can achieve the same effect as the embodiment shown inFIG. 2.

When the heat pump apparatus as described above is fabricated, theinside of the shell case 11 of the compressor 1 which is set to theinner intermediate pressure is vacuum-evacuated, and then refrigerant issealingly filled in the refrigerating cycle. When the shell case 11 isvacuum-evacuated, the vacuum-evacuation is carried out from any one orboth of the suction port of the first stage and the discharge port ofthe second stage, however, in any case, the working is difficult.

In this embodiment, the defrosting intermediate electromagnetic valve231 is provided in the bypass 232, and thus the vacuum-evacuation can becarried out from this site. Accordingly, the vacuum-evacuation of theinside of the shell case 11 is easily performed, the residual amount ofimpurity gas in the refrigerating cycle is reduced, deterioration ofdurability of the refrigerating-machine oil circulated in therefrigerating cycle is suppressed, and the durability of the compressor1 can be enhanced.

FIG. 4 shows another embodiment.

This embodiment has substantially the same construction as theembodiment shown in FIG. 3, and differs in the construction that notall, but a part of the refrigerant of the first stage of the compressor1 is supplied into the shell case 11, and the remaining refrigerant isdirectly supplied from the discharge port 15B of the first stage througha pipe path 51 to the suction port 17A of the second stage. Thisconstruction can provide substantially the same effect as the embodimentas described above. The compressor of this embodiment may be applied tothe defrosting circuit shown in FIG. 1, the defrosting circuit shown inFIG. 2, etc.

As described above, the present invention have been described on thebasis of the embodiments, however, it is apparent that the presentinvention is not limited to these embodiments.

INDUSTRIAL APPLICABILITY

As described above, the present invention is suitably applied to a heatpump apparatus which can perform an efficient defrosting operation whenan internal intermediate pressure two-stage compression type compressoris used.

1. A heat pump apparatus having a refrigerating cycle comprising: acompressor, a gas cooler, a pressure reducing device, and an evaporatorin which water can be heated by the gas cooler, wherein said compressorcomprises a two-stage compression type rotary compressor having a shellcase, an electric motor portion and a compressing portion driven by theelectric motor portion, the electric motor portion and the compressingportion being accommodated in said shell case, and the compressorportion having a two-stage structure including a first-stage compressingportion and a second-stage compressing portion which are mounted in theshell case, wherein at least a part of refrigerant compressed to anintermediate pressure in the first-stage compressing portion is passedthrough said shell case to the second-stage compressing portion andcompressed to a high pressure in the second-stage compressing portion,and the high-pressure refrigerant is discharged from the second-stagecompressing portion to the outside of said shell case, and wherein saidheat pump apparatus further comprises a defrosting circuit for leadingthe intermediate-pressure refrigerant from the first-stage compressingportion of said compressor to said evaporator with bypassing said gascooler and said pressure reducing device.
 2. The heat pump apparatus asclaimed in claim 1, further including a high-pressure defrosting circuitfor leading the high-pressure refrigerant of the second stage of saidcompressor to said evaporator while bypassing said gas cooler and saidpressure reducing device.
 3. The heat pump apparatus as claimed in claim1, wherein refrigerant that works in a supercritical area at ahigh-pressure side is filled and used in the refrigerating cycle.
 4. Theheat pump apparatus as claimed in claim 1, wherein the refrigerant isCO₂ refrigerant.
 5. The heat pump apparatus as claimed in claim 1,wherein said defrosting circuit is equipped with an opening/closingvalve with which the inside of said shell case of said compressor can bevacuum-evacuated.
 6. A heat pump apparatus having a refrigerating cycleincluding a compressor, a gas cooler, a pressure reducing device and anevaporator in which water can be heated by the gas cooler, wherein saidcompressor comprises a two-stage compressor for leading at least a partof refrigerant compressed to an intermediate pressure at a first stagethrough a shell case to a second stage, means for compressing theintermediate-pressure refrigerant to a high pressure at a second stageand discharging the high-pressure refrigerant, said heat pump apparatusfurther including a defrosting circuit for leading theintermediate-pressure refrigerant from the first stage of saidcompressor to said evaporator with bypassing said gas cooler and saidpressure reducing device, and wherein the mixing ratio of oil in theintermediate-pressure refrigerant of the first stage is smaller than themixing ratio of oil in the high-pressure refrigerant of the secondstage.
 7. A heat pump apparatus having a refrigerating cycle comprises:a compressor, a gas cooler, a pressure reducing device, and anevaporator in which water can be heated by the gas cooler, wherein saidcompressor comprises a two-stage compression type rotary compressorhaving a shell case, an electric motor portion and a compressing portiondriven by the electric motor portion, the electric motor portion and thecompressing portion being accommodated in said shell case, and thecompressor portion having a two-stage structure including a first-stagecompressing portion and a second-stage compressing portion which aremounted in the shell case, wherein at least a part of refrigerantcompressed to an intermediate pressure in the first-stage compressingportion is passed through said shell case to the second-stagecompressing portion and compressed to a high pressure in thesecond-stage compressing portion, and the high-pressure refrigerant isdischarged from the second-stage compressing portion to the outside ofsaid shell case, and wherein said heat pump apparatus further comprisesa defrosting circuit for selectively leading at least one of theintermediate-pressure refrigerant of the first-stage of said compressorand the high-pressure refrigerant of the second-stage to said evaporatorwhile bypassing said gas cooler and said pressure reducing device. 8.The heat pump apparatus as claimed in claim 7, wherein the refrigerantis CO₂ refrigerant.
 9. The heat pump apparatus as claimed in claim 7,wherein said defrosting circuit is equipped with an opening/closingvalve with which the inside of said shell case of said compressor can bevacuum-evacuated.
 10. A heat pump apparatus having a refrigerating cycleincluding a compressor, a gas cooler, a pressure reducing device and anevaporator in which water can be heated by the gas cooler, whereinrefrigerant that works in a supercritical area at a high pressure sideis filled and used in said refrigerating cycle, said compressor having ashell case comprises a two-stage compressor for leading at least a partof refrigerant compressed to an intermediate pressure at a first stagethrough said shell case to a second stage, means for compressing theintermediate-pressure refrigerant to a high pressure at the second stageand discharging the high-pressure refrigerant, said heat pump apparatusfurther including a defrosting circuit for selectively leading at leastone of the intermediate-pressure refrigerant of the first stage of saidcompressor and the high pressure refrigerant of the second stage to saidevaporator while bypassing said gas cooler and said pressure reducingdevice, and wherein the mixing ratio of oil in the intermediate-pressurerefrigerant of the first stage is smaller than the mixing ratio of oilin the high-pressure refrigerant of the second stage.